TrES-2b (also known as Kepler-1b or GSC 03549-02811b) is an

extrasolar planet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first detect ...

orbiting the star

GSC 03549-02811 GSC 03549-02811 (sometimes referred to as Kepler-1, or either TrES-2A or TrES-2 parent star in reference to its exoplanet TrES-2b) is a binary star system containing a G-type main-sequence star, G-type main sequence, main-sequence star si ...

located 750

light year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distance, astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by t ...

s away from the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

. The planet was identified in 2011 as the darkest known

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...

, reflecting less than 1% of any light that hits it. Reflecting less light than charcoal, on the surface the planet is said to be pitch black, although, given its closeness to its parent star, it would still visually have a very high surface brightness. The planet's mass and radius indicate that it is a

gas giant A gas giant is a giant planet composed mainly of hydrogen and helium. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" was originally synonymous with "giant planet". However, in the 1990s, it became known that Uranu ...

with a bulk composition similar to that of

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

. Unlike Jupiter, but similar to many planets detected around other stars, TrES-2b is located very close to its star and belongs to the class of planets known as

hot Jupiter Hot Jupiters (sometimes called hot Saturns) are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter (i.e. Jupiter analogue, Jupiter analogues) but that have very short orbital periods (). The close proximity to t ...

s. This system was within the

field of view The field of view (FOV) is the angle, angular extent of the observable world that is visual perception, seen at any given moment. In the case of optical instruments or sensors, it is a solid angle through which a detector is sensitive to elec ...

of the ''Kepler'' spacecraft. This planet continues to be studied by other projects, and the parameters are continuously improving. A 2007 study improved stellar and planetary parameters. A 2008 study concluded that the TrES-2 system is a

binary star A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...

system. This significantly affects the values for the stellar and the planetary parameters.

Discovery

TrES-2b was discovered on August 21, 2006 by the

Trans-Atlantic Exoplanet Survey The Trans-Atlantic Exoplanet Survey, or ''TrES'', used three 4-inch (10 cm) telescopes located at Lowell Observatory, Palomar Observatory, and Teide Observatory to locate exoplanets. It was made using the network of small, relatively inexpens ...

(TrES) by detecting the

transit Transit may refer to: Arts and entertainment Film * ''Transit'' (1980 film), a 1980 Israeli film * ''Transit'' (1986 film), a Canadian short film * ''Transit'' (2005 film), a film produced by MTV and Staying-Alive about four people in countrie ...

of the planet across its parent star using Sleuth (

Palomar Observatory The Palomar Observatory is an astronomical research observatory in the Palomar Mountains of San Diego County, California, United States. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observat ...

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

) and PSST (

Lowell Observatory Lowell Observatory is an astronomical observatory in Flagstaff, Arizona, United States. Lowell Observatory was established in 1894, placing it among the oldest observatories in the United States, and was designated a National Historic Landmark ...

Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...

), part of the TrES network of 10–cm telescopes. The discovery was confirmed by the

W. M. Keck Observatory The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes have aperture primary mirrors, and, when c ...

on September 8, 2006, by measuring the radial velocity of the star that hosts TrES-2b.

Spin-orbit angle

In August 2008 more details of the relationship between the parent star and the orbit of the planet were published. The orbit was determined to be tilted by − from the stellar equator. The orbital direction was determined to be in the same direction as the star's rotation (prograde).

''Kepler'' mission

NASA launched ''Kepler'' in March 2009. The spacecraft is dedicated to the discovery of extrasolar planets by the

transit method Methods of detecting exoplanets usually rely on indirect strategies – that is, they do not directly image the planet but deduce its existence from another signal. Any planet is an extremely faint light source compared to its parent star. For e ...

from

solar orbit A heliocentric orbit (also called circumsolar orbit) is an orbit around the barycenter of the Solar System, which is usually located within or very near the surface of the Sun. All planets, comets, and asteroids in the Solar System, and the Sun i ...

. In April 2009 the project released the first light images from the spacecraft, and TrES-2b was one of two objects highlighted in these images. Although TrES-2b is not the only known exoplanet in the field of view of this spacecraft it is the only one identified in the first light images. This object is important for calibration and check-out. Kepler First Light Detail TrES-2

The Kepler mission also managed to detect the mass of the planet from Kepler data alone through the analysis of the light curve of the host star. In addition to detecting the planet directly, the planet was also detected by analysis of the star brightness caused by the gravitational tug of TrES-2b by shape distortion of the host star and by light variations due to Doppler beaming.

Physical characteristics

Albedo

The first important result from the Kepler Mission about TrES-2b is an extremely low

geometric albedo In astronomy, the geometric albedo of a celestial body is the ratio of its actual brightness as seen from the light source (i.e. at zero phase angle (astronomy), phase angle) to that of an ''idealized'' flat, fully reflecting, diffuse reflection, d ...

measured in 2011, making it the intrinsically darkest known exoplanet. If the entire day–night contrast were due to geometric albedo, it would be 2.53%, but modeling suggests that much of this is dayside emission and the true albedo is much lower. It is estimated to be less than 1%, and for the best-fit model, it is about 0.04%. This makes TrES-2b the darkest known exoplanet, reflecting less of the light that strikes it than coal or black acrylic paint. It is not clear why the planet is so dark. One reason could be the absence of reflective clouds such as those that make Jupiter so bright due to TrES-2b's proximity to its parent star and the consequent high temperature. Another reason could be the presence in the atmosphere of light-absorbing chemicals such as vaporized sodium, potassium, or gaseous titanium oxide; however, Kipping and Spiegel excluded heavy oxides of titanium and

vanadium Vanadium is a chemical element; it has Symbol (chemistry), symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an ...

from their models, as it seems unrealistic that condensed, heavy compounds be present in the upper atmosphere. They also note that in general, hot Jupiters are expected to be dark, because "absorption due to the broad wings of the sodium and potassium D lines is thought to dominate their visible spectra", and, apart from that of

Kepler-7b Kepler-7b is one of the first five exoplanets to be confirmed by NASA's Kepler spacecraft, and was confirmed during the first 34 days of Kepler's science operations. It orbits a star slightly hotter and significantly larger than the Sun that is e ...

(), albedo measurements for hot Jupiters have generally given only upper limits.

Temperature

The planet is likely to be tidally locked to the parent star. In 2015, the planetary nightside temperature was estimated to be equal to 1885 K.

Notes

References

External links

Host to 'Hot Jupiter' (labeled)
NASA, 2009-04-16

* ttp://www.perseus.gr/Astro-Photometry-TrES-2-20120529.htm Light curve for TrES-2b using differential photometry {{DEFAULTSORT:TrES-2b Exoplanets with Kepler designations Draco (constellation) Exoplanets discovered in 2006 Giant planets Hot Jupiters Transiting exoplanets